Lost Mountain is an isolated height in southeastern Oklahoma, northwest of Antlers in Pushmataha County, geographically part of the Kiamichi Mountains but set apart in the Kiamichi River valley. Though its 791-foot summit falls below a strict mountain benchmark, its prominence comes from rising alone from the valley floor, with the river wrapping around much of its base and Spirit Lake bordering another side. It was once tied to the nearby boomtown of Kosoma, later a ghost town, and to the St. Louis and San Francisco Railway, which carried timber from the area. In the early 20th century, a religious commune occupied the summit, leaving hand-dug wells behind.